The invention relates to a brake disk/hub assembly for vehicle disk brakes, particularly for commercial vehicles, having a hub and a brake disk non-rotatably arranged thereon.
Vehicle disk brakes of this type are used particularly when a uniform braking effect is to be implemented with a good proportioning capability. For this purpose, the brake disk is normally pushed axially onto the brake disk hub, which is frequently also a wheel hub of the vehicle, and is secured. For this purpose, the hub has a cross-sectional design on its outer circumferential surface which is not circular, but preferably has a tooth-shaped contour. In the area of its passage opening, the brake disk has a complementary construction so that a form-closure is obtained which does not permit a mutual rotation of these components and by which the braking torque is therefore transmitted from the brake disk to the hub.
The axial securing of such brake disks on a hub can take place in different fashions. Thus, for example, German Patent Document DE 198 39 844 A1 discloses a brake disk and a pertaining axle hub, in which case the brake disk is coupled by screws to the hub such that it is not axially movable. However, this construction method, which constructively is very simple and reliable per se, has the disadvantage that it allows no compensation of tolerances. This may have a negative influence on the braking behavior as well as on the useful life of the braking elements and of the bearing.
Another method of construction of a brake disk/hub assembly is known from German Patent Document DE 198 39 763 A1. Here also, the brake disk is pushed in a form-locking manner on to and over the hub. Radially externally projecting collars formed on the cams of the hub are used as a stop for the brake disk in the axial direction. In addition, intermediate elements are arranged radially between the hub and the brake disk or on the circumferential side between the cams of the hub and the supporting elements of the brake disk. The torque and force transmission takes place by way of the intermediate elements during the braking operation. The axial fixing of the brake disk on the side situated away from the collars takes place by using a retaining ring. The retaining ring is inserted into a ring grove on the hub and projects radially to the outside such that the brake disk is thereby held in a form-locking manner in the axial direction. As a rule, a slight play of the brake disk exists here in the axial direction, so that a compensating movement can take place in this direction. However, as a result, shock-like loads and more or less controlled movements of the brake disk are also possible which, in turn, has a disadvantageous effect on the useful life of the components.
Furthermore, a brake disk/hub assembly has become known from International Patent Document WO 97/48 919. Here, the brake disk is fixed in the axial direction on one side by a rigid stop in the form of a retaining ring and, on the other side, by a spring-elastic retaining ring. In this case, the spring-elastic retaining ring is constructed in a fully surrounding manner and is screwed to the hub. It has a plurality of bearing surfaces which are distributed on the circumference side and are in contact with the lateral surface of the brake disk. The fastening of this spring-elastic retaining ring to the wheel hub in this construction takes place at a desired large distance from the bearing surfaces on the brake disk, so that a predetermined and not too short spring travel occurs; that is, an axial moving possibility of the brake disk. An axial displacement of the brake disk is therefore possible only against this spring force, in which case shock loads must therefore be buffered and absorbed.
However, this method of construction also has disadvantages. Thus, in the case of external shock loads or large deflections from the normal position, the spring-elastic retaining spring may break as soon as its elastic deforming range has been exceeded. Furthermore, the spring-elastic retaining ring is subjected to considerable thermal loads, which originate from the brake disk which heats up considerably during the braking operation. This thermal load results in a change of the characteristics of the material of the spring-elastic retaining ring and, particularly, of the spring characteristics. Thus, the conditions in this range, that is, the possible axial play of the brake disk during a braking operation, can change because of the thermal effect, so that the brake arrangement becomes less predictable and reliable. The useful life of this spring-elastic retaining ring is therefore relatively low.
It is therefore an object of the invention to further develop a brake disk/hub assembly of the above-mentioned type for vehicle disk brakes, particularly for commercial vehicles, such that the loading of the spring device can be minimized and the reliability of the vehicle disk brake can thereby be increased.
This object is achieved by distributing and arranging a plurality of intermediate elements on an inner circumferential side of the brake disk radially between the hub and the brake disk. A spring device has a plurality of spring elements. Each spring element includes a holding section by which it is fixed on the hub, and at least one spring section supported on at least one assigned intermediate element. The brake disk is axially displaceable against a spring-elastic pretensioning applied by the spring device.
Thus, it is provided according to the invention that a plurality of intermediate elements is arranged which, distributed about the circumference, are each arranged radially between the hub and the brake disk, and in that the spring device has a plurality of spring elements, each spring element having a holding section by which it is fixed to the hub, and at least one spring section which is supported on at least one assigned intermediate element. According to the invention, it is thereby achieved for the first time that the elements of the spring device are no longer directly supported on the brake disk, but rather on the intermediate elements. As a result, the thermal loading of the spring device can be clearly reduced. Simultaneously, a play-free coupling of the brake disk to the hub can be achieved in the unloaded condition, in which case axial forces, if necessary, will be elastically absorbed so that a shock-like loading can be avoided.
Because the spring device has a plurality of spring elements, a still better compensation of manufacturing tolerances, etc. can be achieved. Each spring element acts alone and is unaffected by the adjacent spring element. Should a spring element be damaged, possibly also by an external effect, the other spring elements remain unaffected, that is, as a rule, the damage will not affect the adjacent spring element. The operational reliability or protection against breakdown of the arrangement, as a whole, is therefore increased.
The brake disk/hub assembly according to the invention, while it has a simple construction, is therefore characterized particularly in that the spring device is better protected from thermal and mechanical loads and therefore has a longer useful life.
Advantageous further developments of the invention are described herein.
Thus, a spring device can be arranged on one side of the brake disk, while a fixed stop exists on the other side. This significantly simplifies, in particular, the mounting of the brake disk/hub assembly according to the invention since there a few individual elements and the mounting can take place from one side. However, as an alternative, it is also possible to provide a spring device on both sides of the brake disk.
When the axial displacement of the brake disk is limited to a predetermined extent by a stop device, it can effectively be prevented that the spring device is mechanically overloaded; that is, that a deformation takes place beyond an elastic deformation limit. This further increases the reliability of the arrangement.
In this case, the stop device can be constructed by the holding section of each spring element, so that an additional constructional element can be eliminated. This results in a further simplification, particularly of the mounting. The force in the axial direction, which occurs in this case, will then be absorbed by the fastening device by which the holding section is fixed to the hub.
Thus, the holding section of each spring element can be fixed, for example, by using a screw, on a respective cam of the hub, whereby a reliable connection can be established using devices known per se and therefore in a cost-effective manner.
It is also advantageous for each spring element to have a passage opening with an internal thread through which the screw is screwed for producing a captive preassembled unit, and for each cam in the axial direction of the hub to have an internal thread as well as a duct of a sufficient length for the screw to reach the thread. The screw has a thread-free barrel section as well as a threaded section of a length which is smaller than the length of the duct plus the material thickness of the spring element. As a result of the preassembly of the screw and the spring element permitted thereby, the main mounting of the brake disk/hub assembly according to the invention can be significantly simplified. It is also important in this case that the thread section of the screw is limited to a predetermined length so that the spring element can be placed on the intermediate elements on the brake disk at the desired point and only then does the screw have to be screwed into the cam. The spring element can therefore be positioned before it is fastened.
Furthermore, each spring element can have two spring sections, which extend in opposite directions away from the holding section, so that no one-sided loading occurs at the holding section. The additional advantage that a spring-elastic support can be provided simultaneously at two points can also be achieved in this manner. This further reduces the number of constructional elements whereby the mounting expenditures are reduced.
In addition, each spring element may have a supporting section which is radially supported on the brake disk. This prevents rotation of the spring element when the screws or the like are tightened. This is particularly advantageous when the screw and the spring element are provided as a captive preassembled unit.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.